1. Field
The disclosed concept pertains generally to electrical switching apparatus and, more particularly, to mechanisms for circuit interrupters. The disclosed concept also pertains to resettable trip indicator mechanisms for circuit interrupters. The disclosed concept further pertains to circuit interrupters.
2. Background Information
Circuit interrupters, such as for example and without limitation, circuit breakers, are used to protect electrical circuitry from damage due to an overcurrent condition, such as an overload condition, a short circuit or another fault condition, such as an arc fault or a ground fault. Molded case circuit breakers typically include at least one pair of separable contacts per phase. The separable contacts may be operated either manually by way of a handle disposed on the outside of the case or automatically in response to a detected fault condition. Typically, such circuit breakers include an operating mechanism, which is designed to rapidly open and close the separable contacts, and a trip mechanism, such as a trip unit, which senses a number of fault conditions to trip the breaker automatically. Upon sensing a fault condition, the trip unit trips the operating mechanism to a trip state, which moves the separable contacts to their open position.
It is known to hold a trip shaft in a rotated position when a circuit breaker is tripped. For example, some power circuit breakers employ a Resettable Trip Indicator (RTI) to signal a user that the circuit breaker has tripped due to an overload condition. In many instances, the circuit breaker is inoperable until the RTI is reset. For example, the RTI is often used in the IEC (European) market, while the UL/ANSI (United States) market often employs a Trip Indicator (TI).
Both of the RTI and TI provide an indication that a circuit breaker tripped as a result of an overload (e.g., short circuit) in an electrical system. For example, an RTI or TI push button/indicator can be a suitable color (e.g., red), such that when it pops-up it becomes clearly visible since it protrudes above the circuit breaker front cover.
It is a good practice to reset the TI push button/indicator by pressing the push button down from the popped-up position after removing the overload (e.g., short circuit) condition. However, the TI does not require being reset since the circuit breaker remains fully functional regardless of the TI position (e.g., reset or popped-up). Conversely, the RTI is required to be reset (e.g. by pushing the RTI push button down from the popped-up position), in order to enable the circuit breaker to close, since the RTI push button holds a trip shaft in a rotated position after the circuit breaker is tripped. This prevents the circuit breaker from closing until the trip shaft returns to its initial, non-rotated position.
In some known circuit breakers, a trip actuator is employed to unlatch an operating mechanism and trip open separable contacts in response to an overcurrent condition. For example, the trip actuator trips the circuit breaker by extending a plunger, which, in turn rotates a trip shaft. As soon as the trip actuator plunger is extended, the circuit breaker cannot be closed. For example, some of these known circuit breakers reset the trip state and return the trip actuator plunger to a retracted position by pushing a trip indicator rod. Others of these known circuit breakers are reset by other mechanisms (e.g., by an “opening yoke”). The “opening yoke” resets the trip actuator every time when the circuit breaker trips. In other words, the trip actuator trips the circuit breaker (e.g., by extending the trip actuator plunger). The “opening yoke” (during the tripping operation) resets the trip actuator (e.g., by pushing the trip actuator plunger back in its retracted position). In this case, the trip shaft is held in a rotated tripped position by a special linkage and not by the trip actuator plunger.
There is room for improvement in mechanisms for circuit interrupters.
There is also room for improvement in resettable trip indicator mechanisms for circuit interrupters.
There is further room for improvement in circuit interrupters including resettable trip indicator mechanisms.